Report by E.P.A. Offers Heartening News on Summertime Air

By MICHAEL JANOFSKY

Published: August 19, 2005

A new report by the Environmental Protection Agency says ozone levels are falling in 19 Eastern states where bad air is common in the summer.

The reduction reflects what agency officials describe as a significant decline in emissions of nitrogen oxides, whose reaction with sunlight, other weather conditions and volatile organic chemicals can make the air hard to breathe in the warmer months.

The report says that last year, nitrogen oxide emissions from power plants and other large sources of combustion in the 19 states, including New York, New Jersey and Connecticut, were 30 percent below 2003 levels and 50 percent below those of 2000. The result, it says, was a four-year reduction in ozone of about 10 percent.

Jeffrey R. Holmstead, who is stepping down on Friday as the agency's assistant administrator for air and radiation, said that ''this is a very significant reduction of ozone concentration'' and that it offers reassurance ''that what we're working on is the effective way to go.''

Mr. Holmstead was referring to the cap-and-trade approach to emission reduction, which is favored by the Bush administration, rather than the Clinton administration's absolute cap, which remains favored by environmentalists.

In a cap-and-trade system, a plant can exceed its permitted level of emissions by buying credits from a plant in the same region whose emissions are below what is allowed. Environmentalists argue that such an approach fails to achieve the lowest possible emissions, because it does not require all plants to use ''best available control technology.''

But Mr. Holmstead said cap-and-trade worked more efficiently, since plant owners, without enough money to make all the necessary improvements at once, had incentive to install controls on the biggest emission sources first.

Responding to the new report, Frank O'Donnell, president of Clean Air Watch, an environmental group that monitors federal policy, acknowledged that ''it's fair to say we are making progress.''

''At the same time,'' Mr. O'Donnell added, ''we haven't solved the ozone problem. This summer's air pollution shows how much further we have to go.''

The report deals with one part of the Bush administration's broader strategy to combat air pollution under the Clean Air Act. Two larger components made final this year -- the Clean Air Interstate Rule, governing nitrogen oxides and sulfur dioxide, and new standards for mercury emission controls -- are intended to apply to 30 states and the District of Columbia.